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SubjectRe: [PATCH 8/9] pstore/blk: use the normal block device I/O path
On Fri, Oct 16, 2020 at 03:20:46PM +0200, Christoph Hellwig wrote:
> Stop poking into block layer internals and just open the block device
> file an use kernel_read and kernel_write on it. Note that this means
> the transformation from name_to_dev_t can't be used anymore, and proper
> block device file names must be used.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> [...]
> +
> +#ifdef MODULE
> +static int __init pstore_blk_init(void)
> +{
> + return __pstore_blk_init(blkdev);
> +}
> late_initcall(pstore_blk_init);
>
> static void __exit pstore_blk_exit(void)
> {
> - if (!psblk_bdev)
> + if (!psblk_file)
> return;
> unregister_pstore_device(&pstore_blk_zone_ops);
> - blkdev_put(psblk_bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
> + fput(psblk_file);
> }
> module_exit(pstore_blk_exit);
> +#else /* MODULE */
> +/*
> + * During early boot the real root file system hasn't been mounted yet,
> + * and not device nodes are present yet. Use the same scheme to find
> + * the device that we use for mounting the root file system.
> + */
> +void __init pstore_blk_early_init(void)
> +{
> + const char devname[] = "/dev/pstore-blk";
> + dev_t dev = name_to_dev_t(blkdev);
> +
> + if (!dev)
> + return;
> + init_unlink(devname);
> + init_mknod(devname, S_IFBLK | 0600, new_encode_dev(dev));
> + __pstore_blk_init(devname);
> +}
> +#endif /* MODULE */

That the allowed naming conventions change based on _how_ pstore is
built seems very wrong to me.

While I do like the clean up to simplify the read/write activities, this
seems like totally the wrong approach here.

>
> /* get information of pstore/blk */
> int pstore_blk_get_config(struct pstore_blk_config *info)
> diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
> index 0abd412a6cb3e3..7c06b9d6740e2a 100644
> --- a/include/linux/pstore_blk.h
> +++ b/include/linux/pstore_blk.h
> @@ -39,4 +39,6 @@ struct pstore_blk_config {
> */
> int pstore_blk_get_config(struct pstore_blk_config *info);
>
> +void __init pstore_blk_early_init(void);
> +
> #endif
> diff --git a/init/main.c b/init/main.c
> index 1af84337cb18d5..058cce64f70390 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -98,6 +98,7 @@
> #include <linux/mem_encrypt.h>
> #include <linux/kcsan.h>
> #include <linux/init_syscalls.h>
> +#include <linux/pstore_blk.h>
>
> #include <asm/io.h>
> #include <asm/bugs.h>
> @@ -1524,6 +1525,9 @@ static noinline void __init kernel_init_freeable(void)
> prepare_namespace();
> }
>
> + if (IS_BUILTIN(CONFIG_PSTORE_BLK))
> + pstore_blk_early_init();
> +

I hate this being a special-case in kernel_init. For ramoops, we use:

postcore_initcall(ramoops_init);

which is much better than open coding this here.

> /*
> * Ok, we have completed the initial bootup, and
> * we're essentially up and running. Get rid of the
> --
> 2.28.0
>

--
Kees Cook

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